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| Dr. Beate Ritz |
When Dr. Beate Ritz was in psychiatric training in Germany, her 62-years-old department chair suddenly developed Parkinson’s disease. The rapid progression of his symptoms left her searching for answers.
“When I asked what causes Parkinson’s, the answer was always, ‘We don’t know,’” Ritz said. That question inspired her to spend more than 20 years studying how the environment, including pesticides and pollution, might play a role in the disease.
Her research led her to California’s Central Valley, one of the nation’s agricultural powerhouses. There, Ritz began to piece together troubling evidence: links between pesticide exposure, air pollution, and the risk of Parkinson’s disease.
Pesticides and Parkinson’s
The first hints came in the 1980s with the infamous case of the “frozen addicts.” Drug users injected a synthetic heroin contaminated with a chemical similar to paraquat dichloride, a widely used herbicide. Within days, they developed Parkinson’s-like symptoms.
Ritz used California’s unique Pesticide Use Reports, which track what chemicals are sprayed, where, and when. Her studies revealed that paraquat exposure through inhalation of pesticide drift or ingestion via dust and water was strongly associated with a heightened risk of Parkinson’s disease.
Subsequent animal studies reinforced her findings, showing paraquat could trigger the same kind of damage to dopamine-producing neurons seen in patients. “We are now basically convinced that paraquat can cause Parkinson’s,” Ritz said.
Her team has since identified more than ten additional pesticides that are directly toxic to neurons. Current studies are examining how combinations of these chemicals may amplify harm.
Air pollution and neurodegeneration
Ritz’s research soon expanded beyond pesticides. She began looking at traffic-related pollutants such as carbon monoxide and fine particulate matter dust-sized particles that can infiltrate the body and brain.
These pollutants contain metals and can heighten inflammation, processes tied to immune dysfunction in Parkinson’s disease. One pathway of particular interest: the nose. Loss of smell often precedes diagnosis, and Ritz theorizes that nanoparticles from pollution may travel directly from the nasal passages to the brain’s olfactory bulb, sparking early disease processes.
But pollution research is fraught with complexity. “We have to consider pollution sources, co-exposures, comorbidities and individual vulnerabilities,” she cautioned.
Building a registry and a community
When Ritz began her work, California had no data on Parkinson’s cases. She lobbied for a patient registry, joined by colleagues and advocacy groups. In 2004, the state passed legislation mandating reporting. After funding was secured in 2017, nearly 1,000 Central Valley patients enrolled in UCLA-led studies, along with an equal number of community members serving as controls.
The registry not only advanced science but also gave patients a sense of solidarity. Ritz’s team sends annual updates even Christmas cards to thank participants and share progress. “They feel they are suffering quietly and alone,” Ritz said. “This helps them feel part of something bigger.”
Toward policy change
Ritz’s work has pushed the science closer to causation, but translating findings into policy remains difficult. She argues that understanding cellular “fingerprints” of pesticide exposure may provide the evidence needed to drive regulatory action.
Her analysis suggests that reducing pesticide use near communities could be a cost-effective way to lower the burden of Parkinson’s. Yet change faces resistance from powerful agricultural interests.
California is more proactive than most states in regulating pesticides, but paraquat banned in more than 70 countries is still widely used in the U.S. Legal battles may prove to be the tipping point. Ritz serves as an expert witness in lawsuits alleging that paraquat exposure contributed to Parkinson’s disease.
“Industry responds in two ways: either through bans, which take years, or through lawsuits,” Ritz explained.
For now, her research continues, driven by the same question she asked as a trainee: Why does Parkinson’s develop? And can understanding its environmental triggers bring the world closer to prevention?
As paraquat and other chemicals remain in use, Ritz’s 25 years of work stand as both a warning and a roadmap a reminder that what we spray on fields may eventually take root in the brain.
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